The invention relates to a method for fitting and removing a vehicle brake master cylinder and in particular a master cylinder intended to be mounted on a braking assistance servo unit of a motor vehicle.
The master cylinders known in the prior art include a spring, called a secondary spring, located in the barrel between the bottom of the barrel and the secondary piston. The function of this spring is to push back the secondary piston toward the primary piston and therefore to push back the secondary piston/primary piston assembly toward the mouth of the barrel.
When the master cylinder is not mounted on the braking assistance servo unit, this spring therefore has a tendency to push back the primary piston/secondary piston assembly toward the outside of the barrel of the master cylinder.
When the master cylinder is removed, there is a risk that this spring may eject the master cylinder mechanism assembly toward the outside of the latter. There is therefore a risk of damaging the inside parts of the master cylinder or losing some of them.
To prevent that, according to a known technology, the secondary spring is provided with a mechanism to limit its travel. FIG. 1 illustrates an example of such a device. The axial barrel of the master cylinder contains the primary pp and secondary ps pistons in a manner known in the prior art. A primary spring r1 is interposed between the two pistons. A secondary spring r2 is interposed between the secondary piston ps and the bottom MCf of the barrel of the master cylinder. The assembly is inserted in the barrel of the master cylinder via the mouth MCe of the barrel. The spring rs2 bears on the bottom MCf of the barrel and tends to push back the pistons toward the outside of the barrel.
In the system in FIG. 1, the travel of the secondary spring r2 is limited by two cups c1 and c2 which slide on a rod t1. The rod t1 is provided with two collars e1 and e2 which prevent the cups from moving away from each other by more than a certain distance. This system thus limits the travel of the secondary spring r2.
The invention relates to a system making it possible to dispense with such a device for limiting the travel of the secondary spring.
It therefore provides a simplified master cylinder compared with prior art master cylinders.
The invention relates to a method for fitting and removing a master cylinder which comprises a primary piston and a secondary piston which are mounted in a barrel of the master cylinder with at least one spring placed between the bottom of the barrel and the secondary piston and having the function of pushing back the secondary piston and the primary piston toward the mouth of the barrel. According to the invention, the secondary spring is free and the method comprises at least the following step: installation of a temporary retaining pin in an access hole located on the periphery of the master cylinder so that the pin emerges inside the barrel between the mouth of the barrel and either the primary or the secondary piston. Advantageously, this pin is installed temporarily.